Seals are used to prevent leakage between two environments. Seals can be used, for example, to retain a fluid, separate fluids or to prevent the transmission of particulate contaminants from one environment to another. A static seal would completely prevent leakage if the contacting surfaces were perfectly smooth or if the asperities in contact are heavily deformed and sufficiently flattened.
Seals can also be used in non-static devices such as rolling element bearings, or to seal the gap between a shaft and the bore of bearing housing. An example of a typical elastomeric lip seal is shown in FIG. 1. Non-static devices rely on seals to retain lubricant and prevent the ingress of water and particulate contaminants, such as grit. They also rely on an extremely thin elasto-hydrodynamic film between the seal and the moving surface to prevent excessive wear of the seal, particularly on start-up when slow movement leads to large frictional forces and the seal is most prone to wear.
It is known that seals account for the major part of friction in a sealed bearing. For instance, lip seals can account for approximately 75% of the total bearing power loss in a bearing run under typical application conditions at a load of 1015 N (C/P=20), speed of 3000 rpm and grease lubrication. As there are hundreds of billions of rubber seals used worldwide, which are running 24 hours per day and 365 days every year, the total energy consumption of the rubber seals is enormous. Reduction of friction torque induced by the rubber seals would thus lead to significant energy savings.
Accordingly, there is a desire for a seal that will overcome, or at least mitigate, some or all of the problems associated with the seals of the prior art, or at least provide a useful or optimized alternative.